Question: lazy result set

[jgeraerts]

With postgresql (probably other databases as well) you can set the fetch-size on a statement to the result set will not be pulled in 1 go into the client. This is useful if you have large result sets you need to process record by record. With plain clojure.java.jdbc you would do that like

(jdbc/with-db-transaction [tx connection]
  (jdbc/query tx
    [(jdbc/prepare-statement (:connection tx)
                              "select * from tablewithmanyrecords"
                              {:fetch-size 10})]
     {:result-set-fn (fn [result-set] ...)}))

https://jdbc.postgresql.org/documentation/94/query.html#query-with-cursor

It's a bit unclear how I would do something similar with hugsql.

[achikin]

+1 does hugsql have any support for cursors?

[tmountain]

Would also like to know the answer to this question.

[node13h]

+1

[si-robinson]

+1

[ctdean]

Any news on this feature?

[frankleonrose]

This works for me, given a sqlvec-query and side-effecting-fn to do something with each result.

(jdbc/with-db-transaction [tx *db*]
  (let [results (jdbc/reducible-query tx sqlvec-query {:fetch-size 1000})]
     (transduce (map side-effecting-fn) (constantly nil) results)))